1. Field of the Invention
The present invention relates to a method of making a window frame used suitably for a window panel for vehicles or buildings, and a method of making a window panel with a window frame.
2. Description of Related Art
There is a case that a window frame for a front glass of a vehicle is provided with a rain gutter at its side portion to provide a flow passage for rain. The rain gutter is to prevent the eyesight of a driver from decreasing by the deposition of rain drops scattering from the sides of the front glass onto the side windows. However, it is unnecessary to form the rain gutter in the upper side portion of the window frame.
In a conventional technique, window frames having different shapes in cross section were separately prepared for the upper peripheral portion and side peripheral portions of the front glass, and the window frames were joined interposing a joint in one piece at a portion corresponding to a corner of the front glass by using a compression or an injection molding method. Therefore, the position of the joined portions was conspicuous. Further, the color tone and the gloss of the window frame were non-uniform because the parts of the window frame were separately prepared. In addition, the joined portions may be broken, or noises may be produced due to the vibrations of the vehicle during driving.
In order to eliminate the above-mentioned problems, a method of making a window frame of a one-piece body without a joined portion was proposed in U.S. Pat. No. 5,167,893 and U.S. Pat. No. 5,174,623. According to the proposal, a shutter is provided in front of an extrusion-molding die to open and close slowly an opening portion of the die so that a rain gutter is gradually formed in and disappears from the window frame. However, in such method, the cross-sectional shape of the window frame is changed by closing a part of the opening of the die. At the opening of the die, a resistance takes place in resin in a portion in contact with the shutter, and no resistance takes place in the resin at a portion which does not contact to the shutter. Then there is a difference of speed in the resin to be extruded depending on the presence or the absence of the resistance, whereby a shaped product is bent to the side of the shutter, and a stable shaping is difficult to obtain. Further, when a high viscous material is used, shaping of the window frame is difficult because the shape of the window frame is changed at the outlet of the die.